Many female contestants who appear on the BBC Two show presented by Jeremy Paxman are reportedly targeted by viewers through cyber hate campaigns, some of which depict them in sexual fantasies.

The majority of those who appear on the cult show are aged between 18 and 21 and the cream of the crop – those students who are crowned University Challenge champions – are destined for glittering careers.

But some who appear on the quiz, due to celebrate its 50th anniversary next year, have suggested that all is not as it seems behind the scenes amid claims the audience is prejudiced against women.

Officials behind the show, produced for the BBC by ITV studios - formerly Granada Productions - admit that after appearing on the programme, some have been "the subject of unwanted attention".

Producers say the students, who are selected following rigorous tests of their general knowledge, are given detailed briefings about how to handle some of the negative aspects of fame.

More than 2.5 million viewers tune in every week to watch the show with previous contestants including Stephen Fry, the actor and Julian Fellowes, the writer.

One unnamed student who appeared on the quiz, first broadcast in 1962, had to ask the studio's legal department, to remove personal pictures from a blog post that showed her alongside images of male genitalia.

Other contestants have pleaded for advice after they were subjected to viewer criticisms including what they wore, how they spoke and how nervous they appeared.

Jenny Harris, 22, who won the show last year as part of the team from Emmanuel College, Cambridge, said she was uncomfortable with the coverage she received.

She suggested the show's audience was prejudiced against female contestants.

"People can get almost a personal outrage if University Challenge women do not meet their standards of attractiveness, or nastily personal comments if they do," she told The Independent.

"An aspect of it is the idea that women shouldn't be showing off how clever they are, where this is more OK for boys.

"The fact that there are fewer women in pretty much every match, it looks like a male-dominated environment and is judged by the standards of one."

Marine Debray, 20, who represented Balliol College, Oxford, on the show admitted she had "a pretty awful experience" after her episode was broadcast.

"I got lots of friend requests on Facebook, loads of emails and had to turn up my privacy settings so that I couldn't be found online," she said.

"There was a guy who made a photo album of me intercut with photos of a penis.

"But my mentality was that it'll be over in five days and then they'll have someone new to latch on to – which turned out to be true."

She added: "We all know what happens when you go on national TV. But people seemed to think that because I wasn't this nerdy male then I shouldn't be on there.

"Look at how Gail Trimble [a former contestant] was asked to pose for Nuts. Just because a woman's smart doesn't mean that she has to show you her b ... s."

In 2008 Corpus Christi College beat Manchester University in the final with their captain Miss Trimble, the Oxford Latin scholar dubbed "human Google", who won many plaudits.

But it then emerged that fellow team member Sam Kay had graduated and was working as a trainee accountant. Corpus Christi was stripped of the title.

Miss Trimble later became a victim of a hate campaign through Facebook, the social networking site and other internet blogs.

In the wake of the scandal the BBC issued tough new guidelines for teams entering the challenge. It was the first time the BBC has changed the regulations since the show began in 1962.

A spokesman for ITV Studios said on Wednesday that contestants who were targeted by viewers were offered full support.

She said the organisation was "aware that some of our contestants are the subject of unwanted attention".

"As a much-loved television show University Challenge attracts a great deal of attention, most of which is supportive of the competing teams and individual contestants," she said.

" Before they take part in the programme team members are briefed about the possibility of media attention, including online, and are provided with the contact details of a member of the University Challenge team who is available to offer advice and support.

"They are fully briefed in advance of broadcast and provided with a number that we encourage them to call in these situations. There is a system in place to deal with such events."